1. Field of the Invention
The invention relates to an imaging optical system, and more particularly, to a subminiature imaging optical system which is suitably applicable to a subminiature optical device such as a mobile phone camera.
2. Description of the Related Art
In general, mobile phones featured only a communicative function at an incipient stage. However, with their use broadened, various services such as photographing or image transmission or communication have been in demand, accordingly evolving the function and services thereof. Recently, the spotlight has been given to a new concept of mobile phones, so-called, camera phones or camera mobile phones integrating digital camera technology with mobile phone technology. Moreover, under development have been so-called camcorder mobile phones or camcorder phones which incorporate digital camcorder technology into mobile phone technology to store and transmit video multimedia running for at least ten minutes.
Lately, cameras installed in the mobile phones are required to possess capability of electronic still cameras. Also, photographing lenses face a fierce demand for smaller size, lighter weight and lower cost. Charge-coupled Devices (CCDs) or Complimentary Metal Oxide Semiconductors (CMOSs) in current use are increasingly reduced in their sizes so that the imaging optical system using this imaging device needs to demonstrate high-definition.
Furthermore, the photographing lenses installed in the mobile phones should be less numbered to achieve miniaturization and low cost, which however accompanies limited flexibility in design and unsatisfactory optical capability.
Therefore, this calls for a high-definite subminiature imaging optical system.